It varies. I had my son's first one done and it was $350 if I remember correctly. Have heard as high as $600. I'm in middle TN so no help on a taxidermist your way.
Mark Driver, Tennessee River Taxidermy, does great work. He uses freeze dried heads, not fake heads. He is great with feathers. He has done five birds for me and family.
$400 would be the absolute minimum for a quality strutting turkey with no base or habitat. Anything less and you run the risk of taking forever or wasting your money. Some exceptions do exist, but rarely. Do not be surprised at someone charging $600-$800(or more)for one.
Have you considered a nice panel or a cape/wing mount?